A) Field of Invention
The present invention relates to a fluid sealing device for use with a motor, and more particularly to a fluid sealing device for use with a motor for rotating a disc drive.
B) Description of Related Art
Numerous fluid sealing devices for use with motors for rotating disc drives have been proposed. For example, various embodiments of known fluid sealing devices are shown in abandoned U.S. patent application Ser. No. 08/438,953, which was filed on May 11, 1995, and U.S. patent application Ser. No. 08/442,32 which was filed on May 16, 1995, U.S. Pat. No. 5,675,199.
FIG. 1 of the current application shows a DC motor which uses a known fluid sealing device as described in the '953 application. The motor includes a frame 21 with a center shaft 21a. In this motor, a hub 54 is mounted on the center shaft 21a of the frame 21 by use of bearings 2 and a magnetic bearing fluid 14.
A stator core 6 is fixed to an outer surface of the frame 21 and a coil 5 is wound onto the stator core 6. A drive magnet 7 is attached to an inner periphery of the hub 54 and is positioned to face the stator core 6. One or more discs, which are not shown, are loaded onto the outer periphery of the hub 54. Thus, when a voltage is applied to the coil 5 from an external power source, the hub 54 and associated discs are rotated.
The frame 21 and center shaft 21a are made of a ferromagnetic material. A magnet 30 having an inclined surface 30A is positioned near an open end of the frame 21 to form a magnetic circuit. The magnetic circuit includes the magnet 30, ferromagnetic frame 21 and center shaft 21a, as well as the magnetic bearing fluid 14. This magnetic circuit prevents the magnetic bearing fluid 14 from leaking out of the motor and contaminating the discs.
The DC motor shown in FIG. 1 also includes bearing fluid absorption members 43 which are attached to an upper surface of the magnet 30 and an outer surface of the shaft 21a. Thus, even if the magnetic bearing fluid 14 is not completely contained by a magnetic flux produced from the magnetic circuit, the bearing fluid absorption members 43 will absorb the magnetic fluid and prevent further leakage.
FIG. 2, which is also included in the '953 application, shows a similar fluid sealing device. Under this arrangement, a magnet 31 and ferromagnetic body 35, which is fixed to a center shaft 3, form part of a magnetic circuit to prevent the magnetic bearing fluid 14 from leaking out of the motor and contaminating the discs.
The DC motor shown in FIG. 2 also uses bearing fluid absorption members 43. The bearing fluid absorption members 43 of the device shown in FIG. 2 are also attached to an upper end of a magnet 31 and an outer peripheral surface of a shaft 3. Similar to the device shown in FIG. 1, the bearing fluid absorption members 43 are provided to absorb magnetic bearing fluid which escapes a magnetic flux produced by the magnetic circuit.
FIG. 3, which is described in the '321 application, shows another known configuration of a fluid sealing device for a DC motor. Referring to FIG. 3, a magnet 30, center shaft 3, and bearing 2 form part of a magnetic circuit to prevent the magnetic bearing fluid 14 from leaking from a motor.
A plate 41 is mounted to one end of the magnet 30 adjacent to an open end of the shaft 3 to further prevent the magnetic bearing fluid 14 from leaking. Attached to the plate 41 and the shaft 3 are layers 42 which are made of a slippery material such as TEFLON. The layers 42 cause the magnetic bearing fluid 14 coming into contact with them to form into beads or droplets and thus be returned to the reservoir of magnetic bearing fluid 14.
Bearing fluid absorption members 43 are also provided and positioned on an upper surface of the plate 41 and on the center shaft 3. The bearing fluid absorption members 43 absorb any magnetic bearing fluid 14 which leaks past the magnetic circuit and the layers 42.
During conditions of shock and vibration, the bearing fluid escapes from its reservoir. The devices shown in FIGS. 1 through 3 capture much of the escaped bearing fluid. However, any bearing fluid that is not captured by these devices tends to contaminate the discs affixed to the motor. Thus, there remains a need for an improved bearing fluid sealing device which can more effectively capture and absorb larger amounts of bearing fluid and therefore more effectively prevent bearing fluid from leaking and from contaminating the discs.